Question

20.it was twenty years ago ______ he joined the party.

20.it was twenty years ago ______ he joined the party.
A)as
B)when
C)since
D)that
你好请问答案为什么选D啊，请帮我详细的解答，谢谢~

Answer 1

It is...that... It was ... that...
是强调句型的固定用法。

强调句型
i．强调谓语或者其他成分
1．强调谓语动词一般在谓语动词原型前加do／does／did。时态是一般现在时，在动词原型前加do／does，时态是一般过去时，在谓语动词原型前加did。
2．强调句子其他成分用强调句型：“It+be+被强调成分+关系代词who／that+句子的其他成分”。
注意：
1)被强调的成分是人时，关系代词可以用who／that，强调其他成分时(除谓语动词外)一律用that。
2)在强调句中'be动词通常只有两种形式：一般现在时is，一般过去时was，但是不能排除带有情态动词的形式。

Answer 2

D. that
It was twenty years ago that he joined the party.

Answer 3

这是定语从句。缺少宾语，用which或that